HIV (Human Immunodeficiency Virus (type 1)) belonging to retrovirus is a causative virus of AIDS (Acquired Immunodeficiency Syndrome).
HIV targets CD4 positive cell groups such as helper T cell, macrophage and dendritic cell and destroys these immunocompetent cells to cause immunodeficiency.
Accordingly, a medicament that eradicates HIV in a living organism or suppresses its growth is effective for the prophylaxis or treatment of AIDS.
HIV possesses a bimolecular RNA gene in a shell, which is covered with an envelope protein. The RNA codes for several enzymes (protease, reverse transcriptase, integrase) characteristic of the virus and the like. Translated reverse transcriptase and integrase are present in the shell, and protease is present inside and outside the shell.
HIV contacts and invades a host cell, causes uncoating, and releases a complex of RNA and integrase and the like into the cytoplasm. From the RNA, DNA is transcribed by reverse transcriptase, and a full length double stranded DNA is produced. The DNA moves into the nucleus of the host cell and is incorporated by integrase into the DNA of the host cell. The incorporated DNA is converted to an mRNA by polymerase of the host cell, from which mRNA various proteins necessary for forming a virus are synthesized by HIV protease and the like, and a virus particle is finally formed, which then undergoes budding and its release.
These virus specific enzymes are considered to be essential for the growth of HIV. These enzymes are drawing attention as the target of the development of antiviral agents, and several anti-HIV agents have been already developed.
For example, zidovudine, didanosine, lamivudine and the like have been already on the market as reverse transcriptase inhibitors, and indinavir, nelfinavir and the like as protease inhibitors.
In addition, a multiple drug combination therapy using these medicaments in combination (to be also referred to as HAART (highly active antiretroviral therapy)) is also used. For example, 3 agent combination therapy using two agents from reverse transcriptase inhibitors (zidovudine and lamivudine, or tenofovir and emtricitabine), and a non-nucleic acid reverse transcriptase inhibitor (efavirenz), or a protease inhibitor (lopinavir, fosamprenavir or atazanavir) in combination with ritonavir, and the like is used in clinical practice, and such multiple drug combination therapy is becoming the mainstream of the AIDS treatment.
However, some of these medicaments are known to cause side effects such as liver function failure, central nervous disorders (e.g., vertigo), and the like. In addition, acquisition of resistance to a medicament causes a problem. Even worse, emergence of an HIV that shows multiple drug resistance in a multiple drug combination therapy has been known.
Under the circumstances, a further development of a novel medicament, particularly a development of an anti-HIV agent based on a new mechanism, has been desired, wherein a development of an anti-HIV agent having an integrase inhibitory activity is expected, because an integrase characteristic of retrovirus is an essential enzyme for the growth of HIV.